title: Recognition of the activated states of Galpha13 by the rgRGS domain of PDZRhoGEF.
abstract: G12 class heterotrimeric G proteins stimulate RhoA activation by RGS-RhoGEFs. However, p115RhoGEF is a GTPase Activating Protein (GAP) toward Galpha13, whereas PDZRhoGEF is not. We have characterized the interaction between the PDZRhoGEF rgRGS domain (PRG-rgRGS) and the alpha subunit of G13 and have determined crystal structures of their complexes in both the inactive state bound to GDP and the active states bound to GDP*AlF (transition state) and GTPgammaS (Michaelis complex). PRG-rgRGS interacts extensively with the helical domain and the effector-binding sites on Galpha13 through contacts that are largely conserved in all three nucleotide-bound states, although PRG-rgRGS has highest affinity to the Michaelis complex. An acidic motif in the N terminus of PRG-rgRGS occupies the GAP binding site of Galpha13 and is flexible in the GDP*AlF complex but well ordered in the GTPgammaS complex. Replacement of key residues in this motif with their counterparts in p115RhoGEF confers GAP activity.
authors.affiliation: Department of Pharmacology, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
authors.forename: Zhe
authors.initials: Z
authors.lastname: Chen
authors.forename: William D
authors.initials: WD
authors.lastname: Singer
authors.forename: Shahab M
authors.initials: SM
authors.lastname: Danesh
authors.forename: Paul C
authors.initials: PC
authors.lastname: Sternweis
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Sprang
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D044365:GTP-Binding Protein alpha Subunits, G12-G13 / Q000737:chemistry* / Q000378:metabolism*; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D020710:RGS Proteins / Q000737:chemistry; D051381:Rats; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity / Q000235:genetics
chemical_list: D020690:GTPase-Activating Proteins; D020662:Guanine Nucleotide Exchange Factors; C523071:PDZ-RhoGEF, rat; D020710:RGS Proteins; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D044365:GTP-Binding Protein alpha Subunits, G12-G13